1,925 research outputs found
Holographic Dark Energy Characterized by the Total Comoving Horizon and Insights to Cosmological Constant and Coincidence Problem
The observed acceleration of the present universe is shown to be well
explained by the holographic dark energy characterized by the total comoving
horizon of the universe (HDE). It is of interest to notice that the very
large primordial part of the comoving horizon generated by the inflation of
early universe makes the HDE behave like a cosmological constant. As a
consequence, both the fine-tuning problem and the coincidence problem can
reasonably be understood with the inflationary universe and holographical
principle. We present a systematic analysis and obtain a consistent
cosmological constraint on the HDE model based on the recent cosmological
observations. It is found that the HDE model gives the best-fit result
() and the minimal
which is compatible with for the CDM model.Comment: 17 pages, 4 figures, two eqs. (26)(27) added for the consistent
approximate solution of dark energy in early universe, references added,
published version in PR
Cosmological Constraint and Analysis on Holographic Dark Energy Model Characterized by the Conformal-age-like Length
We present a best-fit analysis on the single-parameter holographic dark
energy model characterized by the conformal-age-like length,
. Based on the Union2 compilation of
557 supernova Ia data, the baryon acoustic oscillation results from the SDSS
DR7 and the cosmic microwave background radiation data from the WMAP7, we show
that the model gives the minimal , which is comparable to
for the CDM model. The single
parameter concerned in the model is found to be . Since the fractional density of dark energy at
, the fraction of dark energy is naturally negligible in the early
universe, at . The resulting constraints on the
present fractional energy density of matter and the equation of state are
\Omega_{m0}=0.286^{+0.019}_{-0.018}^{+0.032}_{-0.028} and
w_{de0}=-1.240^{+0.027}_{-0.027}^{+0.045}_{-0.044} respectively. The model
leads to a slightly larger fraction of matter comparing to the CDM
model. We also provide a systematic analysis on the cosmic evolutions of the
fractional energy density of dark energy, the equation of state of dark energy,
the deceleration parameter and the statefinder. It is noticed that the equation
of state crosses from to , the universe transits from
decelerated expansion () to accelerated expansion () recently, and
the statefinder may serve as a sensitive diagnostic to distinguish the CHDE
model with the CDM model.Comment: 17 pages, 5 figures, minor changes for the fitting data, references
adde
Asymptotic behavior of the order parameter in a stochastic sandpile
We derive the first four terms in a series for the order paramater (the
stationary activity density rho) in the supercritical regime of a
one-dimensional stochastic sandpile; in the two-dimensional case the first
three terms are reported. We reorganize the pertubation theory for the model,
recently derived using a path-integral formalism [R. Dickman e R. Vidigal, J.
Phys. A 35, 7269 (2002)], to obtain an expansion for stationary properties.
Since the process has a strictly conserved particle density p, the Fourier mode
N^{-1} psi_{k=0} -> p, when the number of sites N -> infinity, and so is not a
random variable. Isolating this mode, we obtain a new effective action leading
to an expansion for rho in the parameter kappa = 1/(1+4p). This requires
enumeration and numerical evaluation of more than 200 000 diagrams, for which
task we develop a computational algorithm. Predictions derived from this series
are in good accord with simulation results. We also discuss the nature of
correlation functions and one-site reduced densities in the small-kappa
(large-p) limit.Comment: 18 pages, 5 figure
Antitumor Activity of 2,9-Di-\u3cem\u3eSec\u3c/em\u3e-Butyl-1,10-Phenanthroline
The anti-tumor effect of a chelating phen-based ligand 2,9-di-sec-butyl-1,10-phenanthroline (dsBPT) and its combination with cisplatin were examined in both lung and head and neck cancer cell lines and xenograft animal models in this study. The effects of this agent on cell cycle and apoptosis were investigated. Protein markers relevant to these mechanisms were also assessed. We found that the inhibitory effect of dsBPT on lung and head and neck cancer cell growth (IC50 ranged between 0.1–0.2 μM) was 10 times greater than that on normal epithelial cells. dsBPT alone induced autophagy, G1 cell cycle arrest, and apoptosis. Our in vivo studies indicated that dsBPT inhibited tumor growth in a dose-dependent manner in a head and neck cancer xenograft mouse model. The combination of dsBPT with cisplatin synergistically inhibited cancer cell growth with a combination index of 0.3. Moreover, the combination significantly reduced tumor volume as compared with the untreated control (p = 0.0017) in a head and neck cancer xenograft model. No organ related toxicities were observed in treated animals. Our data suggest that dsBPT is a novel and potent antitumor drug that warrants further preclinical and clinical development either as a single agent or in combination with known chemotherapy drugs such as cisplatin
Critical behaviour of a surface reaction model with infinitely many absorbing states
In a recent letter [J. Phys. A26, L801 (1993)], Yaldram et al. studied the
critical behaviour of a simple lattice gas model of the CO-NO catalytic
reaction. The model exhibits a second order nonequilibrium phase transition
from an active state into one out of infinitely many absorbing states.
Estimates for the critical exponent suggested that the model belongs to
a new universality class. The results reported in this article contradict this
notion, as estimates for various critical exponents show that the model belongs
to the universality class of directed percolation.Comment: 10p+5fig, LaTeX+fig in uuencoded P
Series expansions of the percolation probability for directed square and honeycomb lattices
We have derived long series expansions of the percolation probability for
site and bond percolation on directed square and honeycomb lattices. For the
square bond problem we have extended the series from 41 terms to 54, for the
square site problem from 16 terms to 37, and for the honeycomb bond problem
from 13 terms to 36. Analysis of the series clearly shows that the critical
exponent is the same for all the problems confirming expectations of
universality. For the critical probability and exponent we find in the square
bond case, , , in the
square site case , ,
and in the honeycomb bond case , . In addition we have obtained accurate estimates for the critical
amplitudes. In all cases we find that the leading correction to scaling term is
analytic, i.e., the confluent exponent .Comment: LaTex with epsf, 26 pages, 2 figures and 2 tables in Postscript
format included (uufiled). LaTeX version of tables also included for the
benefit of those without access to PS printers (note that the tables should
be printed in landscape mode). Accepted by J. Phys.
Are Damage Spreading Transitions Generically in the Universality Class of Directed Percolation?
We present numerical evidence for the fact that the damage spreading
transition in the Domany-Kinzel automaton found by Martins {\it et al.} is in
the same universality class as directed percolation. We conjecture that also
other damage spreading transitions should be in this universality class, unless
they coincide with other transitions (as in the Ising model with Glauber
dynamics) and provided the probability for a locally damaged state to become
healed is not zero.Comment: 10 pages, LATE
Oxytocin induces the formation of distinctive cortical representations and cognitions biased toward familiar mice
Social recognition is essential for the formation of social structures. Many times, recognition comes with lesser exploration of familiar animals. This lesser exploration has led to the assumption that recognition may be a habituation memory. The underlying memory mechanisms and the thereby acquired cortical representations of familiar mice have remained largely unknown, however. Here, we introduce an approach directly examining the recognition process from volatile body odors among male mice. We show that volatile body odors emitted by mice are sufficient to identify individuals and that more salience is assigned to familiar mice. Familiarity is encoded by reinforced population responses in two olfactory cortex hubs and communicated to other brain regions. The underlying oxytocin-induced plasticity promotes the separation of the cortical representations of familiar from other mice. In summary, neuronal encoding of familiar animals is distinct and utilizes the cortical representational space more broadly, promoting storage of complex social relationships
Interacting model of new agegraphic dark energy: observational constraints and age problem
Many dark energy models fail to pass the cosmic age test because of the old
quasar APM 08279+5255 at redshift , the CDM model and
holographic dark energy models being no exception. In this paper, we focus on
the topic of age problem in the new agegraphic dark energy (NADE) model. We
determine the age of the universe in the NADE model by fitting the
observational data, including type Ia supernovae (SNIa), baryon acoustic
oscillations (BAO) and the cosmic microwave background (CMB). We find that the
NADE model also faces the challenge of the age problem caused by the old quasar
APM 08279+5255. In order to overcome such a difficulty, we consider the
possible interaction between dark energy and dark matter. We show that this
quasar can be successfully accommodated in the interacting new agegraphic dark
energy (INADE) model at the level under the current observational
constraints.Comment: 12 pages, 5 figures; typos corrected; version for publication in
SCIENCE CHINA Physics, Mechanics & Astronom
Conditions for the freezing phenomena of geometric measure of quantum discord for arbitrary two-qubit X states under non-dissipative dephasing noises
We study the dynamics of geometric measure of quantum discord (GMQD) under
the influences of two local phase damping noises. Consider the two qubits
initially in arbitrary X-states, we find the necessary and sufficient
conditions for which GMQD is unaffected for a finite period. It is further
shown that such results also hold for the non-Markovian dephasing process.Comment: 4 pages, 2 figure
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